The present invention relates to enhanced efficacy antiperspirant salts containing calcium and an amino acid or a hydroxy acid and particularly to stabilized aqueous solutions of such salts. The present invention also embraces methods of making these antiperspirant salts and solutions and compositions containing same.
Enhanced efficacy aluminum and aluminum-zirconium antiperspirant salts are well known and are described, for example, in GB 2,048,229 and U.S. Pat. No. 4,775,528. These salts are generally made by heat treating a relatively dilute solution of the salt (e.g. about 10% by weight) to increase its HPLC peak 4 to peak 3 ratio, then spray drying to a powder. These salts typically have an HPLC peak 4 to peak 3 area ratio of 0.7 or higher, with at least 70% of the aluminum contained in said peaks. However, these enhanced salts are also known to rapidly revert back to their non-enhanced state (for example, as evidenced by an HPLC peak 4 to peak 3 area ratio of 0.3 or less) in aqueous solution, particularly at concentrations greater than 20%. Consequently, the enhanced antiperspirant salts are generally only available in powder form. Moreover, the enhanced salts are generally only formulated into finished formulations as suspended powders in order to retain their enhanced efficacy.
In U.S. Pat. No. 5,330,751, there is disclosed a method of making stable aqueous solutions of enhanced efficacy antiperspirant salts by mixing a relatively low concentration of the salt (5-20%) with monosilicic acid. This method has several disadvantages. It requires relatively low concentrations of the antiperspirant salt and it produces silica as a biproduct, which makes the solution cloudy and is difficult to remove.
In U.S. Pat. No. 5,643,558 there is disclosed a method of preparing a solution of an enhanced efficacy aluminum antiperspirant salt in a polyhydric alcohol by (a) providing an aqueous solution of about 5 to 20% by weight of an enhanced efficacy aluminum antiperspirant salt in water, (b) mixing the aqueous solution with a liquid polyhydric alcohol (e.g. propylene glycol) to provide a mixed solution, and (c) rapidly evaporating the water from the mixed solution under vacuum to provide a liquid polyhydric alcohol solution containing about 20 to 50% enhanced efficacy aluminum antiperspirant salt and about 2 to 16% water, with the balance being said polyhydric alcohol. When an aluminum-zirconium complex is desired in the final product, the zirconium salt can be added at any stage prior to the evaporation step (c). If the water content exceeds 16%, the peak 4 to 3 ratio of the salt deteriorates on storage.
In copending U.S. application Ser. No. 08/881,237 filed on Jun. 25, 1997 by the present inventor, there is disclosed a method of stabilizing an aqueous solution of an enhanced efficacy aluminum or aluminum-zirconium antiperspirant salt against rapid degradation of the HPLC peak 4 to peak 3 area ratio of said salt by adding to said aqueous antiperspirant salt solution an effective amount of a polyhydric alcohol having from 3 to 6 carbon atoms and from 3 to 6 hydroxyl groups to form a stabilized aqueous antiperspirant salt solution. A second disclosed method involves preparing an enhanced efficacy aluminum antiperspirant salt by heating an aqueous solution of an aluminum antiperspirant salt in the presence of a polyhydric alcohol having from 3 to 6 carbon atoms and from 3 to 6 hydroxyl groups at a temperature of at least 50.degree. C. for a time sufficient to convert the salt to an enhanced salt. A third disclosed method is an improvement in the method of making an aluminum hydroxy halide or an aluminum hydroxy nitrate by reacting aluminum with an aqueous solution of aluminum halide or aluminum nitrate (or with aqueous hydrogen halide or nitric acid), wherein the improvement comprises including a polyhydric alcohol having from 3 to 6 carbon atoms and from 3 to 6 hydroxyl groups in the reaction mixture. Also disclosed are compositions produced by the foregoing methods. These include compositions comprising, in percent by weight (USP), about 18 to 45% of an enhanced efficacy aluminum or aluminum-zirconium antiperspirant salt, about 20 to 70% water, and about 5 to 60% of a polyhydric alcohol having from 3 to 6 carbon atoms and from 3 to 6 hydroxyl groups. The HPLC peak 4 to peak 3 area ratio of the antiperspirant salt in these compositions does not degrade as quickly or to as low a point as similar compositions without the polyhydric alcohol.
In U.S. Pat. No. 2,571,030 there are disclosed calcium aluminum basic chloride antiperspirant salts which have less of a deteriorating effect on fabric than aluminum basic chloride (chlorhydroxide). These salts are made by reacting calcium carbonate with aluminum chlorhydroxide or with aluminum chloride and aluminum powder, or by adding calcium chloride dihydrate to aluminum chlorhydroxide. This patent suggests that the antiperspirant salts may have 0.2 to 15 parts by weight of calcium for every 100 parts by weight of aluminum. The salts do not contain any amino acid.
In U.S. Pat. No. 3,979,510 there are disclosed aluminum-zirconium antiperspirant compositions containing aluminum buffering agents to raise the pH. The aluminum buffering agents may include well-known antacid complexes such as hydrated magnesium aluminum sulfate as well as the co-precipitates of aluminum hydroxide with magnesium or calcium carbonate. Examples VIII and XI describe the preparation of solid non-enhanced Al--Zr salts containing 0.6% and 0.2% calcium respectively (Ca:Al+Zr weight ratio is 1:45 and 1:114), but neither salt contains an amino acid.
In U.S. Pat. No. 3,998,788 there are disclosed aluminum-zirconium antiperspirant compositions containing trace amounts of alkaline earth metal salts, particularly calcium or magnesium or both, and preferably magnesium. Generally, the compositions will contain one part alkaline earth metal to 30-1000 parts by weight of aluminum plus zirconium. A solution containing 5-15% aluminum plus zirconium (roughly 10 to 30% active) will contain about 0.001-0.1% alkaline earth metal. Although the patent suggests that the Al-Zr compositions may be buffered with a variety of buffering agents, including urea and water soluble amino acids among others, no compositions containing an amino acid are exemplified. In fact, no Al--Zr composition containing calcium is exemplified.
In U.S. Pat. No. 4,021,536 there are disclosed astringent zirconium compositions containing a magnesium salt, such compositions having a zirconium to magnesium content, expressed as oxides, of about 30:1 to 1:1. The examples of this patent do not disclose any compositions containing aluminum or calcium, although a Zr--Mg salt of the patent was tested against aluminum chlorohydrate and an Al--Zr--gly salt.
In U.S. Pat. No. 4,017,599 there are disclosed aluminum-zirconium antiperspirant complexes buffered with salts of amino acids including hydroxy aluminum glycinates and alkaline and alkaline earth glycinates. This patent suggests that the various alkaline salts, including sodium, potassium, ammonium, magnesium and calcium, are equally suitable. Example V of this patent describes a solid aluminum-zirconium hydroxybromide composition containing 2.24% Al, 31.2% Zr, 28.6% Br, 4.26% glycine, and 1.10% Ca. This composition thus appears to contain about 82% (USP) of non-enhanced active (i.e. Al--Zr--OH--Br with Al:Zr=0.25:1 (mole ratio)) with a Ca:Al+Zr weight ratio of about 1:30.4 and a glycine:Al+Zr weight ratio of about 1:7.8. The extremely low Al:Zr ratio of this salt places it well outside the current FDA monograph.
In CA 1,068,215 there is disclosed a high pay-off antiperspirant stick comprising 5-20% magnesium stearate, 1-5% calcium carbonate, 0-1% mineral oil, 0.1-5% glycine, 0.01-1% deodorant agent, 20-77.8% aluminum chlorhydroxide, 1-10% kaolin, 10-40% rice starch, 0-3% water, and 0.001-1% perfume. The antiperspirant stick is made by making a first blend of the aluminum salt with mineral oil, making a second blend of the rice starch and water, making a third blend of the remaining ingredients, then mixing the three blends and compressing the mixture into a stick.
In WO 96/19228 there are described topical compositions which contain a topical vehicle, a skin irritating ingredient and an anti-irritant amount of an aqueous soluble divalent calcium cation in an amount of 10 mM to 3000 mM. This publication generally suggests a wide variety of topical compositions including sunscreens, insect repellants, shave creams, depilatories, shampoos, permanent wave and hair straightener products, detergents, drug products, antiperspirant and deodorant products, lozenges, mouthwashes, suppositories, etc.
In U.S. Pat. No. 5,534,246 there are disclosed clear water-in-oil antiperspirant emulsions in which the refractive indices of the oil and water phases are matched. A variety of refractive index adjusting compounds are disclosed, one of which is calcium chloride. Examples 5 and 6 disclose aqueous solutions containing, respectively, 32.94% and 36.25% aluminum chlorohydrate and 11.94% and 6.88% calcium chloride.
In U.S. Pat. No. 5,676,936 there are disclosed alcohol based antiperspirant compositions in which the antiperspirant salt is suspended in an alcohol carrier. Prior to addition of the antiperspirant salt, an anti-dissolution agent is incorporated into the alcohol to inhibit dissolution of the antiperspirant salt in the alcohol. The anti-dissolution agent may be a compound having a basic nitrogen function or a basic oxygen function. Compounds having a basic nitrogen function include amino acids. Compounds having a basic oxygen function include inorganic bases such as sodium, potassium, lithium, calcium and magnesium hydroxide.
Michniak, Int'l. J. Cosm. Sci. 3, 29-36 (1981), describes the effect of various polyvalent cations on sweat production using a rat foot pad test. Calcium chloride solution was found to promote sweating. Calcium chloride was also found to reduce the effectiveness of aluminum, lanthanum and zirconium solutions.
It would be highly desirable to provide enhanced efficacy antiperspirant salts which are stable in aqueous solution. This would make it possible to use the enhanced salts in finished formulations that require a soluble salt form, such as the currently attractive clear gel compositions which have been successfully introduced in recent years. It would also be highly desirable to provide a method of making enhanced efficacy antiperspirant salts in concentrated solution--i.e. at salt concentrations greater than 20%. Such a method would be more efficient than current methods, which generally require dilute solutions, thus necessitating removal of large amounts water to obtain the powdered salts.